UAVs are commonly launched from the ground in a manner similar to manned aircraft. For example, for fixed wing UAVs this is in many cases by travelling along the ground powered by an energy source carried by the UAV itself until the vehicle reaches sufficient speed for take-off. For example, the UAV may be powered by a battery to drive a propeller. The UAV is driven along a runway-like surface until it reaches take-off speed at which point lift control surfaces are adjusted to increase the lift and cause the aircraft to take-off.
An alternative approach uses a catapult or rail guided system. In this system, the UAV is driven forward by an elastic or spring mechanism, and the direction of motion is guided by a rail along which the aircraft travels. The rail may be at an angle to horizontal to launch the UAV directly into the air. Catapult systems are generally designed for each specific model or type of UAV.
Other techniques for launching UAVs are also known. FIGS. 1a and 1b show towing systems. FIG. 1a is a winch towing system for gliders (also known as sailplanes). Such towing systems may be used for manned or unmanned gliders. The towline is connected to the aircraft and wound around the winch. As the winch winds in the towline the aircraft is pulled forward at increasing speed. When the aircraft reaches a sufficiently high velocity it is able to take-off.
Other catapult and launch systems use an elastic towline such as a bungee cord coupled to the UAV.
FIG. 1b shows a towing system often used for manned glider or sailplane launch in which a powered aircraft tows the glider. When the glider and powered aircraft reach a desired altitude the towline between the glider and aircraft is released.